Synthetic opioids are compounds that were created to act on the opioid receptors. Novel synthetic opioids include various analogs of fentanyl (e.g., acetylfentanyl, acryloylfentanyl, carfentanil, furanylfentanyl, 4-fluorobutyrylfentanyl or ocfentanil) and newly emerging non-fentanyl compounds with different chemical structures, such as AH-7921, MT-45, and U-47700. In the last years, these drugs have rapidly emerged on the recreational drug market, and their abuse has been increasing worldwide. Due to the high potency and the low dose required to produce desired effects, the risk of overdose for these compounds including severe health implications, is quite high. Several fatal intoxication cases related to the abuse of synthetic opioids have recently been reported in the literature.
As a consequence, the detection of these compounds in biological samples is crucial in order to get a better understanding of their concentration and distribution in body fluids. We overviewed the analytical approaches for the investigation of synthetic opioids in postmortem samples reported in the literature, with special emphasis given to cases of lethal intoxication.